The present invention relates, in general, to a flexible circuit interconnect system and method. More particularly, the invention relates to a system and method of special utility in providing direct electrical contact between a flexible circuit member and a printed circuit board or another flexible circuit.
There are known in the art numerous techniques for providing electrical contact between a number of printed circuit boards or flexible circuit members. However, these techniques have generally fallen into two categories: either the use of an intermediate electrical contact device between the various boards or circuit members; or the use of excessively complex and unduly bulky clamps applied externally to force intimate contact between circuit boards or other circuit members.
U.S. Pat. No. 3,624,587 issued to Conrad on Nov. 30, 1971 for a Clinched-wire Interconnection Device for a Printed Circuit Board illustrates a technique in which a third or intermediate element must be present as an interface between the two printed circuit boards. The receiving board has loops of resilient conductive wire which engage fingerlike insertion strips of a mating printed circuit board. The technique described requires that both circuits be rigid and is simply not applicable where one of the components is a flexible circuit member.
U.S. Pat. No. 3,825,878 issued to Finger et al. on Sept. 10, 1973 for a Flexible Flat Cable System discloses an interconnection technique for a flexible cable. An external housing traps a flexible cable to provide connection to a printed circuit board and provides test point access to the conductors on the board. A flexible cable does not normally have the capability for mounting electronic components as does a flex circuit and the cable is merely a series of electrical conductors. Thus, the cable would comprise a third element for providing electrical interconnection between various circuit members.
U.S. Pat. No. 3,951,493 issued to Kozel et al. on Aug. 14, 1974 for a Flexible Electrical Connector and Method of Making the Same describes a technique in which an intermediate conductive interface is required for interconnecting two rigid printed circuit boards. Conductive strips are placed upon a core of resilient material to provide a flexible interconnection device. The disadvantage of this technique is the requirement for the connector as an additional or intermediate element along the conducting path. Clearly, the more interfaces which are introduced along an electrical path, the less reliable the conducting path becomes.
Similarly, U.S. Pat. No. 4,057,311 issued to Evans on Nov. 11, 1976 for an Elastomeric Connector for Parallel Circuit Boards also requires the interposition of a third circuit or intermediate element between parallel rigid circuit boards. A flexible circuit having closely spaced conductors surrounds an elastomeric body. Contact is made by an external clamp to hold the interface element in compression and establish electrical contact between the printed circuit boards. For the reasons described above, this technique has inherently undesirable aspects and furthermore requires an additional clamping process to establish the interconnection between circuit boards.
A further prior art technique in which no third element is interposed between circuit members is a pressure pad compression contact in which direct contact is provided between a flexible circuit member and a printed circuit board or another flexible circuit. An external clamp composed of screws and a pressure plate are utilized in conjunction with a compression pad to clamp down upon the contacts of the circuit members. This system is unduly complex and costly in manufacture and unnecessarily complicates the interconnection and disassembly of the circuit member elements.